Electric musical instrument



p 1941- G. w. DEMUTH 2,254,840

ELECTRIC MUSICAL INSTRUMENT Filed Sept. 30, 1939 Enventor (IttornegPatented Sept.

Galan w. Demuth, N. 1., assignor to Radio Corporation of America, acorporation of Delaware Application September 30,1939, Serial no;291,230

scum.

This invention relates to an electric musical instrument and moreparticularly to an instrument of the general type oi a vibraharpor chimein which a vibrating "bar is used as a source of the tone. Y In thepresent apparatus,

provided. v

In prior art ,apparatus of the type described, vibrating .members .havebeen provided from which the vibrations could be picked up electriically and the vibrations were produced either mechanically orelectrically. The iorm'of pickups-used were either electromagnetic orelectrostatic. The sounding the vibrating member was accomplished bystriking it with a hammer orplucking \itwith an appropriate pick or, insome instances, by means of an electric driver which caused regenerativeoscillations. In 'the latter form or the deviceflthe" tone builds upgradually and no sharp attack can be secured.

In the striking or pluckingqorms of sounding mechanism, the sharp attackcan be secured, but, when used in conjunction with an electrical pickupand an amplifier, the note sounded at the time oistriking is usuallyquite harsh and containsmany dissonant harmonics.

In, the present apparatus, I provide two me chanically coupled vibratingmembers, one oi which is struck or plucked and the other of which isadapted to operate the electrical pickup. The mechanical couplingbetween the elements is so constructed, preferably by providingconsider- Another object oittheinvention is to provide.

animproved method of actuating the vibrating element'in an instrument oithe class described. Another object of the invention is to provide adouble vibrating element the segments of which may betuned'to'diiierentclosely adiacent irequencies so-..tha.t beats may be secured.

Another. object of the invention is to provide an improved striking.mechanism for electrically striking the-vibratable member with apredetermined force. W, Other and incidental objects of the invention vThe a novel form of vi- 1 brating element is used and a novel method ofstriking or sounding the vibrating element is.

-a readingbi the specification and an inspection V of the accompanyingdrawing in which Figure l is a side view partly in section ,0! one formof the inventionwith a mechanical pluck- 5 ing mechanism; and

Figure 2 is a similar view 6: a second form oi the invention with anelectrical striking mecha-' nism 10 shown in Fig. 1:

The vibrating member is composed of two segments of a bar l0 and H,which are respectively tuned by the adjustable weights 12 and i3 adapted to be secured in appropriate locations on the 15 posed of segments 10and H, is secured in the block II by the screw It or, if desired, thebar may be soldered into the 'block l4 after being located in the properposition. The block I 4 is in turn secured to the relatively heavymembers l5 and I6 which are rigidly securedto the side plates ll and thebase i8. Y

when the member I0 is vibrated transverselm;

a'suflicient quantity of the vibration is transmitted through the blockit to the segment to cause the segment II to vibrate. If the members Illand II are exactly in tune with each othenthe member Ill may be pluckedor struck quite'sharply and the member II, in vibrating insympathytherewith, will produce a uniform vibration without the'sharply.struck note or the dissonant harmonics of the plucked member Hi being(produced thereby. If, however, the members I 0 and II are slightly outof tune with each other, the 'same efiectis produced as far as thestrike note is concerned, but the continued vibrations produce thewell-known effect of beatand the pickup coil 22 willpick up theviebrations oi the segment II as modified by these 40 beats. r The tonein this caseis similar to that 0! a vibraharp or vibraphone. In eithercase,

' the objectionableefiects of the strike note are avoided.

In order to cause vibration of the segment It,

I have provided a cam I! which deflectsand'then suddenly releases theend of the segment ll.

' This cam is may be mounted on an appropriate mounted side by side withappropriate cams ll mounted in such angular relation on the sh'ait'ilasto sired.

produce the tones in any sequenceydemagnetic pickup mechanism is duitesimiwill be apparent'to those skilled in the art upon lar to that shownand' described in my 1 Referring first to the form of the invention barsby the screws in the weights The bar, comtion Serial No. 248,542, filedDecember 30, 1938 (RCV D-6515). In this pickuparrangement, the pickupcoil 22 is mounted on a soft iron member 23, which is magneticallyconnected with and mounted on a small bar magnet 24, preferablyof anappropriate magnetizable alloy. This -magnet 24 is carried 'in asupporting tube 25,

is immediately withdrawn, preventing striking the member ID a secondtime, by the springs 39, carried by. the member 40, and the spring 15,

. which lifts the member 40 when the current ment ll of the vibratablemember may be substantially the same as shown in Fig. 1 and tuned in thesame way by the weight [2. Likewise, the supporting block M, the clampscrew l4, and the massive supporting block l are substantially the same.chanical and electrical shielding, however, I pro-' vide a more massivepartition 32 carried by the side wall l1 and the base 3. The magneticpickup elements 22 to Mi inclusive are likewise similar to thoseillustrated in Fig. 1 and require no further description.

The vibrating element the vibrating element ll. made from an appropriatespringy magnetic material, such as piano wire, and is secured to the endof the segment by means of the block 42 and the screws 43 and 44. Thismember 3i is made very thin in relation to the member ill in order thatvibrations of a considerably greater amplitude may be caused therein.Likewise, the mounting of the block 42 at a slight distance from therigid block l4 tends to increase the amplitude of the vibrations of themember 3|. This member 3|, being very light, is not tuned in the 3| issubstituted for same manner as the segment I I in Fig. 1, but ispreferably tuned by grinding oi the end until the frequency of vibrationis sufiiciently sharpened. If a little too much should happen to beground from the end of the member 3|, the pitch may be slightlyflattened by, for example, afiix ing a small drop of solder which maythen be scraped until it has lowered the pitch only the required amount.The entire connection including the block 42, the screw 44 and the screw43 should, after assembly, be covered with a layer of wax fused intoplace in order to prevent any buzzes or other undesired noises due tothe rela: tive vibration of any of these parts.

The striking mechanism for this form of the invention includes a heavymagnet 34 supportedon appropriate posts 35 and adapted toattract anarmature ,3 6. This magnet and armature may be of the type commerciallyused in relays.

' The armature 36 carries a. bent arm 40 which in turn supports thehammer 33 and the hammer arm 31 by the pivot 38. The hammer arm 31 isheld up against the felt block by an appropriate spring 39. When thecircuit is closed, passing current through the magnet 34, the armature33' is drawn forcibly toward the' magnet, throwing the hammer 33downwardly. When the armature 36 strikes the face of the magnet, thehammer 33, due to its momentum, continues tomove downwardly against thepressure of the spring 39 until it hits the striking member ID. When thehammer 33- strikes the member ID, it bounces and In order to secure moreadequate meversely.

This element 3! is 1. Apparatus of the .class described including avibratable tone-producing member, an electric pickup in cooperativerelation with said member, a second vibratable member in substantialalignment with and coupled to said tone-producing member, massive meansrigidly coupled to said members adjacent their junction point, and meansfor vibrating said second member trans- 2. Apparatus of 'the classdescribed including a vibratable tone-producing member, an electricpickup in cooperative relation with said member, a second vibratablemember coupled to said toneproducing member, and means for vibratingsaid second member transversely, said members being substantially inalignment coupled at their adjacent ends and'having theirouter ends freeto vibrate transversely.

3. Apparatus of the class described including a vibratabletone-producing member, an electric pickup in cooperative relation withsaid member, a second vibratable member coupled to said toneproducingmanner, and means for vibrating said second member transversely, themember in 00- operative relation with said pickup being thirmer than theother member.

4. Apparatus of the class described including a' vibrate transversely,the member in cooperative relation with said pickup being thinner thanthe.

other member. a

5. Apparatus of the class described including a vibratabletone-producing member, an electric pickup in cooperative relation withsaid member,

a second vibratable member coupled to said toneproducing member, meansfor vibrating said second member transversely, the member in cooperativerelation with said pickup being thinner ber, and massive means rigidlycoupled tosaid members adjacent their junction point.

GALAN W. DEMUTH.

